/**
 * 对企业微信发送给企业后台的消息加解密示例代码.
 * 
 * @copyright Copyright (c) 1998-2014 Tencent Inc.
 */

// ------------------------------------------------------------------------

/**
 * 针对org.apache.commons.codec.binary.Base64，
 * 需要导入架包commons-codec-1.9（或commons-codec-1.8等其他版本）
 * 官方下载地址：http://commons.apache.org/proper/commons-codec/download_codec.cgi
 */
package org.ofbiz.wvtools.wxutil.util;

import java.nio.charset.Charset;
import java.util.Arrays;
import java.util.Random;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.apache.commons.codec.binary.Base64;

/**
 * 提供接收和推送给企业微信消息的加解密接口(UTF8编码的字符串).
 * <ol>
 * <li>第三方回复加密消息给企业微信</li>
 * <li>第三方收到企业微信发送的消息，验证消息的安全性，并对消息进行解密。</li>
 * </ol>
 * 说明：异常java.security.InvalidKeyException:illegal Key Size的解决方案
 * <ol>
 * <li>在官方网站下载JCE无限制权限策略文件（JDK7的下载地址：
 * http://www.oracle.com/technetwork/java/javase/downloads/jce-7-download-432124.html</li>
 * <li>下载后解压，可以看到local_policy.jar和US_export_policy.jar以及readme.txt</li>
 * <li>如果安装了JRE，将两个jar文件放到%JRE_HOME%\lib\security目录下覆盖原来的文件</li>
 * <li>如果安装了JDK，将两个jar文件放到%JDK_HOME%\jre\lib\security目录下覆盖原来文件</li>
 * </ol>
 */
public class WXBizMsgCrypt {
    static Charset CHARSET = Charset.forName("utf-8");
    Base64 base64 = new Base64();
    byte[] aesKey;
    String token;
    String receiveid;

    /**
     * 构造函数
     * 
     * @param token          企业微信后台，开发者设置的token
     * @param encodingAesKey 企业微信后台，开发者设置的EncodingAESKey
     * @param receiveid,     不同场景含义不同，详见文档
     * 
     * @throws AesException 执行失败，请查看该异常的错误码和具体的错误信息
     */
    public WXBizMsgCrypt(String token, String encodingAesKey, String receiveid) throws AesException {
	if (encodingAesKey.length() != 43) {
	    throw new AesException(AesException.IllegalAesKey);
	}

	this.token = token;
	this.receiveid = receiveid;
	aesKey = Base64.decodeBase64(encodingAesKey + "=");
    }

    // 生成4个字节的网络字节序
    byte[] getNetworkBytesOrder(int sourceNumber) {
	byte[] orderBytes = new byte[4];
	orderBytes[3] = (byte) (sourceNumber & 0xFF);
	orderBytes[2] = (byte) (sourceNumber >> 8 & 0xFF);
	orderBytes[1] = (byte) (sourceNumber >> 16 & 0xFF);
	orderBytes[0] = (byte) (sourceNumber >> 24 & 0xFF);
	return orderBytes;
    }

    // 还原4个字节的网络字节序
    int recoverNetworkBytesOrder(byte[] orderBytes) {
	int sourceNumber = 0;
	for (int i = 0; i < 4; i++) {
	    sourceNumber <<= 8;
	    sourceNumber |= orderBytes[i] & 0xff;
	}
	return sourceNumber;
    }

    // 随机生成16位字符串
    String getRandomStr() {
	String base = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
	Random random = new Random();
	StringBuffer sb = new StringBuffer();
	for (int i = 0; i < 16; i++) {
	    int number = random.nextInt(base.length());
	    sb.append(base.charAt(number));
	}
	return sb.toString();
    }

    /**
     * 对明文进行加密.
     * 
     * @param text 需要加密的明文
     * @return 加密后base64编码的字符串
     * @throws AesException aes加密失败
     */
    String encrypt(String randomStr, String text) throws AesException {
	ByteGroup byteCollector = new ByteGroup();
	byte[] randomStrBytes = randomStr.getBytes(CHARSET);
	byte[] textBytes = text.getBytes(CHARSET);
	byte[] networkBytesOrder = getNetworkBytesOrder(textBytes.length);
	byte[] receiveidBytes = receiveid.getBytes(CHARSET);

	// randomStr + networkBytesOrder + text + receiveid
	byteCollector.addBytes(randomStrBytes);
	byteCollector.addBytes(networkBytesOrder);
	byteCollector.addBytes(textBytes);
	byteCollector.addBytes(receiveidBytes);

	// ... + pad: 使用自定义的填充方式对明文进行补位填充
	byte[] padBytes = PKCS7Encoder.encode(byteCollector.size());
	byteCollector.addBytes(padBytes);

	// 获得最终的字节流, 未加密
	byte[] unencrypted = byteCollector.toBytes();

	try {
	    // 设置加密模式为AES的CBC模式
	    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
	    SecretKeySpec keySpec = new SecretKeySpec(aesKey, "AES");
	    IvParameterSpec iv = new IvParameterSpec(aesKey, 0, 16);
	    cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);

	    // 加密
	    byte[] encrypted = cipher.doFinal(unencrypted);

	    // 使用BASE64对加密后的字符串进行编码
	    String base64Encrypted = base64.encodeToString(encrypted);

	    return base64Encrypted;
	} catch (Exception e) {
	    e.printStackTrace();
	    throw new AesException(AesException.EncryptAESError);
	}
    }

    /**
     * 对密文进行解密.
     * 
     * @param text 需要解密的密文
     * @return 解密得到的明文
     * @throws AesException aes解密失败
     */
    String decrypt(String text) throws AesException {
	byte[] original;
	try {
	    // 设置解密模式为AES的CBC模式
	    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
	    SecretKeySpec key_spec = new SecretKeySpec(aesKey, "AES");
	    IvParameterSpec iv = new IvParameterSpec(Arrays.copyOfRange(aesKey, 0, 16));
	    cipher.init(Cipher.DECRYPT_MODE, key_spec, iv);
	    // 使用BASE64对密文进行解码
	    byte[] encrypted = Base64.decodeBase64(text);
	    // 解密
	    original = cipher.doFinal(encrypted);
	} catch (Exception e) {
	    e.printStackTrace();
	    throw new AesException(AesException.DecryptAESError);
	}

	String xmlContent, from_receiveid;
	try {
	    // 去除补位字符
	    byte[] bytes = PKCS7Encoder.decode(original);

	    // 分离16位随机字符串,网络字节序和receiveid
	    byte[] networkOrder = Arrays.copyOfRange(bytes, 16, 20);

	    int xmlLength = recoverNetworkBytesOrder(networkOrder);

	    xmlContent = new String(Arrays.copyOfRange(bytes, 20, 20 + xmlLength), CHARSET);
	    from_receiveid = new String(Arrays.copyOfRange(bytes, 20 + xmlLength, bytes.length), CHARSET);
	} catch (Exception e) {
	    e.printStackTrace();
	    throw new AesException(AesException.IllegalBuffer);
	}

	// receiveid不相同的情况
	if (!from_receiveid.equals(receiveid)) {
	    throw new AesException(AesException.ValidateCorpidError);
	}
	return xmlContent;

    }

    /**
     * 将企业微信回复用户的消息加密打包.
     * <ol>
     * <li>对要发送的消息进行AES-CBC加密</li>
     * <li>生成安全签名</li>
     * <li>将消息密文和安全签名打包成xml格式</li>
     * </ol>
     * 
     * @param replyMsg  企业微信待回复用户的消息，xml格式的字符串
     * @param timeStamp 时间戳，可以自己生成，也可以用URL参数的timestamp
     * @param nonce     随机串，可以自己生成，也可以用URL参数的nonce
     * 
     * @return 加密后的可以直接回复用户的密文，包括msg_signature, timestamp, nonce, encrypt的xml格式的字符串
     * @throws AesException 执行失败，请查看该异常的错误码和具体的错误信息
     */
    public String EncryptMsg(String replyMsg, String timeStamp, String nonce) throws AesException {
	// 加密
	String encrypt = encrypt(getRandomStr(), replyMsg);

	// 生成安全签名
	if (timeStamp == "") {
	    timeStamp = Long.toString(System.currentTimeMillis());
	}

	String signature = SHA1.getSHA1(token, timeStamp, nonce, encrypt);

	// System.out.println("发送给平台的签名是: " + signature[1].toString());
	// 生成发送的xml
	String result = XMLParse.generate(encrypt, signature, timeStamp, nonce);
	return result;
    }

    /**
     * 检验消息的真实性，并且获取解密后的明文.
     * <ol>
     * <li>利用收到的密文生成安全签名，进行签名验证</li>
     * <li>若验证通过，则提取xml中的加密消息</li>
     * <li>对消息进行解密</li>
     * </ol>
     * 
     * @param msgSignature 签名串，对应URL参数的msg_signature
     * @param timeStamp    时间戳，对应URL参数的timestamp
     * @param nonce        随机串，对应URL参数的nonce
     * @param postData     密文，对应POST请求的数据
     * 
     * @return 解密后的原文
     * @throws AesException 执行失败，请查看该异常的错误码和具体的错误信息
     */
    public String DecryptMsg(String msgSignature, String timeStamp, String nonce, String postData) throws AesException {

	// 密钥，公众账号的app secret
	// 提取密文
	Object[] encrypt = XMLParse.extract(postData);

	// 验证安全签名
	String signature = SHA1.getSHA1(token, timeStamp, nonce, encrypt[1].toString());

	// 和URL中的签名比较是否相等
	// System.out.println("第三方收到URL中的签名：" + msg_sign);
	// System.out.println("第三方校验签名：" + signature);
	if (!signature.equals(msgSignature)) {
	    throw new AesException(AesException.ValidateSignatureError);
	}

	// 解密
	String result = decrypt(encrypt[1].toString());
	return result;
    }

    /**
     * 验证URL
     * 
     * @param msgSignature 签名串，对应URL参数的msg_signature
     * @param timeStamp    时间戳，对应URL参数的timestamp
     * @param nonce        随机串，对应URL参数的nonce
     * @param echoStr      随机串，对应URL参数的echostr
     * 
     * @return 解密之后的echostr
     * @throws AesException 执行失败，请查看该异常的错误码和具体的错误信息
     */
    public String VerifyURL(String msgSignature, String timeStamp, String nonce, String echoStr) throws AesException {
	String signature = SHA1.getSHA1(token, timeStamp, nonce, echoStr);
	if (!signature.equals(msgSignature)) {
	    throw new AesException(AesException.ValidateSignatureError);
	}

	String result = decrypt(echoStr);
	return result;
    }

}